Adsorption of multiple NO molecules on Au₁₀^- and Au₉Zn^- planar clusters. A comparative DFT study

The doping of atomic clusters with transition-metal atoms modifies to a lesser or greater extent the catalytic properties of the pure forms. Here we study by means of density functional theory (DFT) the adsorption of up to six NO molecules on Au₁₀^- and Au₉Zn^- clusters, both with well-tested D_3h planar geometry, to learn how precise modifications of the atomic and electronic environment, namely one atom and a valence electron, affect the bonding of multiple NO molecules to anionic gold clusters. First, we confirm that these clusters have D_3h symmetry as determined by L. S. Wang and coworkers using photoelectron spectroscopy experiments [Kulichenko et al., J. Phys. Chem. A, 2021, 125, 4606]. Second, we verify that Au₁₀(NO)^- with n ≤ 6 does not form adsorbed (NO)₂ dimers, as realized by the experiments of Ma and coworkers [Ma et al., Phys. Chem. Chem. Phys., 2020, 22, 25227] using a mini flow-tube reactor at 150 K. Third, we discover that the ground state of the doped Au₉Zn(NO)₆^- compound forms a (NO)₂cis-dimer bridging two non-corner Au atoms of the Au₉Zn(NO)₄^- compound. The discussion of adsorption energies, spin multiplicities, bond lengths, charge trends, vibrational strength frequencies of adsorbed NO's, and projected density of states (PDOS), brings additional testable differences between Au₁₀(NO)^- and Au₉Zn(NO)^- compounds (n ≤ 6).